In physics, energy is the quantitative property that must be transferred to a body or physical system to perform work on the body, or to heat it. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement in the International System of Units (SI) of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of one metre against a force of one newton.
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature.
Mass and energy are closely related. Due to mass–energy equivalence, any object that has mass when stationary (called rest mass) also has an equivalent amount of energy whose form is called rest energy, and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy. For example, after heating an object, its increase in energy could be measured as a small increase in mass, with a sensitive enough scale.
Living organisms require energy to stay alive, such as the energy humans get from food. Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the Sun and the geothermal energy contained within the earth.
Many of you would have heard about physical energy levels. Like maintaining the physical energy throughout the day so that you do not get tired. People recommend exercising, meditating etc etc.
But I found out that my mental energy drains at a very rapid rate. I wake up with full energy but...
I'm looking at Schutz 7.4 where first he obtains the following expression for a geodesic:
$$ m \frac {dp_\beta} {d\tau} = \frac 1 2 g_{\nu\alpha,\beta } p^\nu p^\alpha $$
This means that if all the components of ##g_{\nu\alpha }## are constant for a given ##\beta##, then ##p_\beta## is also...
a) So far, I have equated Ek to Eg to solve for h. 1/2(m)(27)^2 = m(9.8)h. I haven't taken the angle into consideration. I'm not sure if I have to use the x or y component. I got my answer to be 37m but again I don't believe this is correct.
b) I did Ek = Eg + Ek. 1/2(m)(27)^2 = m(9.8)(3.5) +...
Hello.
I have a question about the law of energy conservation in GR.
As time is inhmogeneous, we don't have energy-momentum 4-vector which would be preserved during system's dynamical change. It is only possible to define 4-vector locally. And next, the problem regarding how to sum this vectors...
Hi,
When regarding Gravitational Potential Energy, I know the formula is U=mgh. However, when the object is on an incline (say at an angle of 52 degrees) would it still be mgh or something else? (This isn't homework I simply was just curious).
I am interested in energy flux density from the Moon at Earth’s surface, specifically in infrared (albeit most of it comes in infrared anyway).
Physics.SX (boyfarrell) gives an estimate 89 mW/m². I doubt it for several reasons.
400 K (as effective mean) on Moon seems to be unrealistically hot...
The wave function or Schroedinger equation is timeless, correct? You can reverse the equations and forward it.
Our arrow of time comes due to decoherence in macroscopic object.
How about energy bands in solid state. Do you consider it as timeless wave function, or is it decohered?
Table:
To solve, using the conservation of energy:
E0=(m(deutron)+m(16O)-m(17O)-m(p))c^2
so:
E0=(2.014+15.994-16.999-1.008)931.5=0.93 MeV.
so using the conservation of energy:
14.95+0.93=16.62+0+E'
E'=- 0.74 MeV
But the energy sign has become negative. I also calculated for the first excited...
Hi! Hope I'm posting this in the right place! I'm practicing for exams and came over this question:
A proton with mass ##m_p## is accelerated to a relativistic velocity, with kinetic energy ##K##. It collides completely inelastic with another proton, which has the same kinetic energy, ##K##...
Like an electric field is applying a sort of force on a particle. I was wondering if this at all impacts the potential energy of a particle. For instance, when the force of gravity does work on an object, its potential energy changes as a consequence. Would it be the same thing here?
I am given the answer is 2J and I know how to get there with U = q^2/2C. But what I don't understand is that why is the energy not conserved here? How can energy loses just because the capacitance is doubled?
I think I have a rough idea about it, but I am not sure whether it is correct. At least I feel that my understanding is a bit vague. Here it is:
Globally (I mean across all worlds), the energy is conserved because the universal wavefunction evolves strictly according to Schrodinger equation...
So Ekf-Eki+Epf-Epi=0. I understand that the final potential energy is 0 (distance away approaches infinity), but don't get why the final kinetic energy becomes 0. If the final kinetic energy was 0, wouldn't that mean the object no longer has any velocity and would start being effected by the...
Hi, my question is that what is the main challenge of high energy physics? what is the best theory that maybe explain it and why it would not be accepted?
Hello there, I have a question regarding this problem. I have no problem with part A. However, in part B, my solution manual states that the hollow cylinder will reach the bottom last. Why is it? I mean shouldn't the solid cylinder and the hollow one reach the bottom at the same time? you know...
I have used the heat equation and am not able to get the initial heat. This is what I have so far:
81060 = 7 * 140 * (change in temp) - (7 * 11300) + 7 * 140 ( change in temp)
I found the change in temp to be 81.71K. But that does not help me with the initial temperature!
I have often read that dark matter and dark energy are now thought to comprise 94% of the total mass of the Universe. Just now I was reading an article which says that dark energy comprises 74% of the total. So, I'm confused about how energy can comprise mass. Dark matter, I can understand -...
I understand that the mass is being converted to energy but isn't it just an destructive interference of the properties of particles being present as waves of possibility , for example when electron is Interference with it self is it produce energy?,
because the particle are weaves in quantum...
I want to know the difference between potential and potential energy. The potential is measured in volts and we provide potential ex 12V to a circuit. Some times we also say a potential energy to be applied to the electron ex. 1eV etc. I know eV is energy, but my question is do we need to...
m1v1+m2v2=m1vs'+m2v2' , if car hits small fluffy object m2, initially v2=0, and v1'=v2' ... so
m1v1=[m1+m2](v2')
but why not energy? Why is there a KElost?
.5m1v1^2+.5m2v2^2=.5m1v1'^2+.5m2v'2^2 +KElost , and again v2=0, v1'=v2'
.5m1v1^2=.5[m1+m2]v2'^2+KElost
using consv of momentum...
I was just reading about the LIGO experiment wherein an interferometer was used to detect gravity waves. This interferometer uses opposed light waves, detecting if there is a shift in their wavelength due to stretching/squeezing of a gravity wave passing through the lasers. (I hope I'm saying...
Hello,
Trivial question: a system is isolated and all its internal forces are conservative. Because of Newton's 3rd law, all internal forces are pairwise and the net internal force is always zero (regardless of the forces being conservative or not) hence the system's total momentum is conserved...
Hi!.. As known, a certain amount of energy is applied for compressing a mechanical spring. Thus mechanical spring is charged with energy and it stores it as elastic-potential energy. But whole energy, applied for compressing spring, can not be converted into potential energy. The reason is...
Hi Pf
I read that in the light propagator there are loops of electrons. What would be the consequences if
we could switch them off (or neglect them)? would it modify the speed of the photons?
the answer in the solution book is 29K which only comes if I use mass for only one atom. ( They did not show any working )
My attempt:
1/2 x (1.67 x 10^(-27)) x (355)^(2) = 3/2 x 1.38 x 10^(-23) x T
T = 29.48820652 K
The confusion arises when I tried the following question:
Q. Estimate the...
as I read here
http://www.bbc.com/earth/story/20160429-the-real-reasons-nothing-can-ever-go-faster-than-light#:~:text=But%20light%20is%20made%20up,when%20particles%20like%20electrons%20cannot%3F&text=The%20natural%20energy%20they%20possess,are%20already%20at%20top%20speed.
things with mass...
Summary:: Calculate the amount of energy in joules generated from 2 kg of uranium fuel if the uranium 235 represents 0.7% of the metal and every fission releases 200 MeV.
Hi!
I am stuck in this question from my exercise book :
Q. Calculate the amount of energy in joules generated from 2 kg...
Hi,
Planck's equation is written as E=hν where "E" is energy of a photon, "h" is Planck's constant having value 6.626 070 15 x 10-34 Js, and "ν", Greek letter nu, is frequency.
Violet color has frequency range between 790–666 THz (Tera =10^12). If a violet photon of frequency 7.5 x 10^14 Hz...
I don't need the whole answer just a few tips to do it. I think it's something with the two different radiuses, but I'm really bad at this.
We did a similar one in class, but there is a trick in this one that I can't figure out.
I am learning about capillary action of water. As water moves up paper. How is that not violating energy conservation as it is going against the force of gravity. This obviously can't be infinite energy.
So what I did first was calculate the initial and final potential energies with Epi=-9.433*10^11 m and Epf = -1.503*10^12 m.
Then I found change in potential energy, -5.597*10^11 m.
Using this I determined the change in kinetic energy, 5.597*10^11. I then added this change to the initial...
Hello,
I would like to review and validate some concepts that I have been recently thinking about. Hope this is correct and useful to others that need to refresh these concepts.
Forces can be classified as either conservative or nonconservative. Dissipative forces are always nonconservative...
Good day everyone,
I've recently been researching direct energy conversion schemes for nuclear fission, and I have a question on the basic physics behind the device (specifically on how it converts kinetic energy to electricity).
In essence, the "basic" scheme for fission DEC devices is that...
I know I'm probably overcomplicating this question, but I'm having a bit of difficulty coming up with a singular answer. I have a 4-foot diameter flywheel that I need to turn with an electric motor of an unknown horsepower. I say unknown because I I don't know what I need based upon the...
First, it is easy to see that n=4 after the collision because:
E_1=-13.6\frac{1^2}{1^2}eV=-13.6eV
E_4=-13.6\frac{1^2}{4^2}eV=-0.85eV
E_5=-13.6\frac{z^2}{5^2}eV=-0.544eVBut, I never saw a definition for the width of an energy level.
I tried to use something I saw online that said it was...
(a) Using COE,
$$mgh = 0.5mv^2 + 0.5I\omega^2$$
I solved it, where $$\omega = 112 rad/s$$
(b) This is the part where I have question or problem.
I saw my course mate working and he start of with finding centripetal acceleration.
$$a_c = \frac{v^2}{r} = \frac{(r_0\omega)^2}{R_0}$$
Why isn't it...
1. If today vacuum and matter contribute 71 % and 29 % to the total energy density of the universe, at what redshift z were they contributing equally?
2. If today vacuum, matter, and radiation contribute 71 %, 29 %, and 0.01% to the total energy density of the universe, at what redshift z were...
The speed of star on the outer of are solar system is not according to the visible mass.
Change the law of gravitation F = 1/r^2 to fix this.
Galaxies far away are moving away with increasing speed.
Change the law of gravitation F = 1/r^2 to fix this, include a repulsive force to fix.
Would this...
From my understanding, quantum fluctuations create particle pairs that are usually annihilated. Is it possible to use some kind of force (eg: electromagnetism) to direct and separate antiparticles from normal particles?
I believe experiments have proven that it is possible to store positrons...
I know that when it is ΔG>0 , it means there is no spontaneity, when ΔG=0 there is equilibrium, and when ΔG<0, there is spontaneity. But what happens when this is in the context of partial molar properties, when G is molar?
I suppose molar ΔG is referred to a solution. Right? In that case, is...
Hello Forum,
Energy, like space and time, is a common concept but little understood. I think Feynman himself stated energy is hard to describe...
I have a few observations in regards to energy and I would like your feedback on them:
While force, which represents an interaction between two...
Hi,
I am calculating the binding energy of 11- Na- 18
Stats:
Table of nuclides has BE/A = 6.202276 ± 0.006249 MeV
m used = 18.026878252 amu
E= mc^2 answer = 5.894327537620224 MeV
Semi Empirical Answer = 5.919667778950925 MeV
Including excess mass in E = mc^2 method
1 - Calculate...
First time posting in this part of the website, I apologize in advance if my formatting is off.
This isn't quite a homework question so much as me trying to reason through the work in a way that quickly makes sense in my head. I am posting in hopes that someone can tell me if my reasoning is...